Optical fibres are frequently installed with the use of installation tubes. Here, in the first step of the installation process, an installation tube is positioned between two locations to carry an optical fibre to the desired destination. As the installation tube is put in place, the curvature of the tube at any specific position may be reviewed, ensuring the radius of curvature does not extend beyond the operational limits of the optical fibre to be inserted. In this way, the reliability of the optical fibre may be improved.
Subsequently, the optical fibre is fed through the installation tube. The optical fibre may be fed through the installation tube using a variety of methods, for example via traditional cable pulling using a winch line. However, more recently, cable jetting or blowing has also been used to feed optical fibres through an installation line.
In the process of cable jetting, the optical fibre is blown through the installation tube with the use of compressed air. Here, compressed air is introduced at an opening in the installation tube, such that it flows along the installation tube at high speed. Where the optical fibre is inserted into the installation tube, the high-speed air propels the optical fibre due to both the associated drag forces and pressure drop along the length of the installation tube. The friction of the optical fibre against the installation tube is reduced by the airflow, which acts as a buffer between the optical fibre and the installation tube.
When using cable jetting or blowing, the airflow expands down the length of the installation tube. As such, the propelling force due to the action of the air is relatively small at the opening, and relatively large at the air exhaust end of the installation tube. To compensate for this effect, a pushing force is often exerted on the optical fibre by supplementary equipment, increasing the maximum jetting distance considerably.
However, using existing techniques, jetting is not suitable for all kinds of optical fibre. For example, the installation of pre-assembled, industry standard, fibre optic interface (SC connectors) via jetting through an installation tube remains an impossibility. Here the large, bulky SC connector (Standard Connector or Subscriber Connector) located at the end or terminus of the optical fibre is too large to enter into the installation tube, and hence the jetting process cannot be used for installation.